Crochet hat size chart and calculator

How to use the hat calculator

1. Choose who the hat is for, or measure the head and type the size. Adjust the height if you want a shorter or longer hat.
2. Pick a fit. Snug and standard beanies are made smaller than the head so they stretch; slouchy hats are roomier and taller.
3. Crochet a small flat swatch in your stitch and count how many stitches and rounds fit in 4 inches.
4. Choose how many stitches go into your first round. The calculator lists every crown round and when to stop increasing.
5. For a ribbed brim, choose it under Brim and set its height. The brim rounds come out of the hat height, so the total stays the same.

How the hat math works

A top-down hat starts as a flat circle. If the first round has 12 stitches, the second has 24, the third 36, and so on, because each round adds the same number of stitches. That keeps the circle flat as it grows.

The calculator uses your gauge and the fit you picked to work out how many stitches the hat needs to go around the head. Then it finds the increase round that comes closest. After the crown, every round has the same number of stitches and the hat grows straight down to the brim. If you enter your row gauge, it also tells you how many even rounds to work to reach the height.

Formulas

• Hat circumference = head × (1 + ease), where ease is negative for a fitted hat.
• Stitches needed = hat circumference × stitches per inch.
• Increase rounds = stitches needed ÷ first-round stitches, rounded.
• Crown width = final circumference ÷ π.
• Total rounds = height × rounds per inch.
• Brim stitches = final stitches × (1 − brim reduction), rounded to an even number.

Worked example: an adult beanie

An adult medium head is about 22 inches. A standard beanie is 6 percent smaller, so the hat should be about 20.7 inches around. At 12 stitches per 4 inches, that's 3 stitches per inch, or about 62 stitches.

Starting with 12 double crochet stitches, round 5 has 60 stitches, which is the closest round. Sixty stitches at 3 per inch makes a hat 20 inches around, and the crown is about 6.4 inches across. With 7 rounds per 4 inches, a 9 inch hat takes 16 rounds: 5 increasing and 11 worked even.

Crochet hat size chart

Head sizes vary from person to person, so measure when you can. The hat column is the standard fitted size, 6 percent smaller than the head.

The crown column is the hat circumference divided by π. It is the width to aim for when you lay the finished crown flat. The calculator rounds to a whole increase round, so your real crown can land a little either side of it.

Crown stitch counts by size

Here is what the calculator gives for each size at three example gauges, all at the standard fit. Each cell shows the stitches in the last increase round, the number of increase rounds and the total rounds to reach the hat height. Your gauge will differ, so enter it above for your own numbers.

Notice how coarse the double crochet steps are. With a 12 stitch start, every increase round adds 12 stitches, which is 4 inches of hat at this gauge. That is why the toddler and child sizes both land on 48 stitches in that column. If the closest round is too far from the size you want, switch to a smaller start, or add or skip a few increases in the last round. Fit changes the count too: at the dc gauge, an adult medium is 60 stitches for a snug fit and 72 for a slouchy one.

Checking the crown as you go

Gauge in the round can drift from a flat swatch, so measure the crown before you stop increasing. Lay it flat and measure straight across the middle. A flat circle's width is its circumference divided by π (about 3.14), so a 20 inch hat needs a crown about 6.4 inches across. The results show this number for your hat. If your crown is short of it, work another increase round; if it's already wider, pull back a round.

How much smaller than the head? Sources disagree

Every hat chart builds in some negative ease, but the amount varies. Joy of Motion Crochet gives a rule of thumb of about 1 inch smaller than the head. Stitches n Scraps uses 1 to 3 inches for adult sizes and 0 to 1 inch for preemies.

This calculator uses percentages, so the ease grows with the head. On a 22 inch adult head, the standard fit takes off 1.3 inches and the snug fit 2.2 inches. On a 12 inch preemie head, the standard fit takes off 0.7 inches. Both land inside the Stitches n Scraps ranges.

Yarn and finish change the answer too. Joy of Motion says a ribbed hat often has extra stretch, so you could take off 2 to 3 inches. Alpaca stretches more than wool or acrylic. A hat lined with fleece should be crocheted slightly bigger, because the lining cuts the stretch. Use the snug fit for very stretchy hats and the relaxed fit for lined ones. Our crochet hat sizing guide explains ease in more depth.

Two crown rules, and why we use π

Joy of Motion and this calculator both find the crown width by dividing the hat circumference by π (3.14). The Crochet Crowd's guide describes it differently: a 5 inch crown gives a hat 10 inches across, or 20 inches around. A flat circle 5 inches across only measures 15.7 inches around, though. A hat that ends up at 20 inches from a 5 inch crown is relying on stretch or on more shaping after the crown. The π rule tells you the flat crown size that matches your target exactly, so it is the safer check.

The same guide makes a point worth keeping: "Age is Not Factored Into Hat Sizes." Children of the same age can have quite different heads, so measure when you can and treat the age labels in the chart as a fallback.

Adding a ribbed brim

Alternating front post and back post double crochet makes a stretchy rib at the bottom of the hat. The pattern repeats over 2 stitches, so the calculator rounds the brim count to an even number. You can also work the brim with fewer stitches for a snugger edge. Enter the percentage and the calculator tells you how many to decrease to in the first brim round.

Tips for a hat that fits

• Try the hat on, or measure it, once the crown is done. It's much easier to rip back a few crown rounds than a finished hat.
• Work a ribbed or front-and-back post stitch brim for extra stretch and a snugger edge.
• Thicker yarn and taller stitches give a looser fabric, so check your gauge whenever you change either.
• If you're making a hat as a gift and can't measure, go a little bigger. A hat that's slightly big is easier to wear than one that's too small.